Drain cleaning devices typically utilize an electric motor that rotates a drum which houses a drain cleaning cable or “snake” as known in the art. A belt is typically used between the motor and drum. As will be appreciated by those skilled in the art, as the drum is rotated, the drain cleaning cable is either advanced or retracted, and rotated about its longitudinal axis. Frequently, it is necessary to adjust the tension of the belt that rotates the drum and administers the drain cleaning cable. A wide assortment of belt tensioning assemblies are known in the art and used in drain cleaning devices. One function of such belt tensioning assemblies is to maintain an effective level of tension on the belt so that the belt does not slip against the drum, and therefore so that the drum is efficiently rotated. However, it is also important that slippage be allowed to occur in the event that the drain cleaning cable abruptly stops or becomes bound, or if rotation of the drum is suddenly precluded.
During operation of a drain cleaning device, it is important that a particular amount of torque is transmitted to the drum and hence to the drain cleaning cable, by the motor and belt. If the level of torque is excessive, the cable will frequently bend and/or buckle in the drum which is undesirable. If the level of torque is too low, the drain cleaning cable will not effectively dislodge or disrupt blockages typically encountered in a drain cleaning operation. And so, another function of many belt tensioning assemblies used in drain cleaning devices is to achieve a particular amount of torque in the rotating drain cleaning cable.
FIGS. 1 and 2 illustrate a typical belt tensioning assembly 10 used in a prior art drain cleaning apparatus 2. The drain cleaning apparatus 2 comprises, in part, a motor 40 that rotates a drive pulley 42, which in turn drives a belt 50. The assembly 10 utilizes an idler pulley assembly 20 that includes a pulley 22 rotatably mounted on an arm 26 by an axle 24. The arm 26 is pivotable about a base 30. Referring to FIG. 1, the assembly 10 also utilizes a tensioning spring 60 affixed to a frame or other stationary member of the drain cleaning apparatus 2 by a spring base 62. As will be understood, the spring 60 urges the pulley 22 against the belt 50.
Operators typically adjust the tension of the belt 50 by trial and error in selecting different springs, such as spring 60. Typically, the tension exerted upon the idler pulley 22 and thus upon the belt 50, can be changed by selecting a spring having a different length and/or a different spring constant. FIGS. 1 and 2 illustrate two different springs 60 and 60′, respectively, used to urge the idler pulley 22 against the belt 50. Operators in the field typically keep a variety of replacement parts including an assortment of springs. And so, in deciding to adjust the belt tension in the apparatus of FIG. 1 for example, an operator must stop the drain cleaning device, remove the spring 60 by disengaging it from the idler pulley assembly 20, remove or loosen the spring base 62, select a new spring, attach the new spring to the idler pulley assembly and the spring base, and then restart the drain cleaning device. After this series of operations, the operator must then determine whether the newly selected spring is imparting the proper amount of tension so as to achieve the desired amount of torque at the drain cleaning cable.
If the operator determines that the newly selected spring is still not resulting in the proper level of torque for the drain cleaning cable, this process must be repeated, i.e. the drain cleaning apparatus stopped, previous spring removed and replaced with a different spring, and then the device restarted. Often several cycles of this process must be undertaken before an operator achieves a desired level of torque at the drain cleaning cable. Understandably, this process is tedious and time consuming.
Another technique used by operators to adjust belt tension is to change the position of the spring base 62. Referring further to FIGS. 1 and 2, it will be understood that the tension of springs 60 and 60′ in FIGS. 1 and 2 can be reduced by moving the spring base 62 from position B to position A on a frame support member thereby reducing the length of the tensioned spring. And, referring to FIG. 2, it will be understood that the tension of spring 60′ can be increased by moving the spring base from position B to position C thereby increasing the length of the tensioned spring.
Although changing the linear position of the spring base from one location to another is less cumbersome and tedious than replacing the entire spring, the technique is limited. First, it is still undesirable to completely disengage an end of the spring from attachment to a stationary member. Such disengagement results in a near entire loss of force application to the belt by the idler pulley. Furthermore, the linear span or range within which the spring base can be moved is typically limited by the exposed area available on the frame support member. Moreover, additional holes must be drilled in the frame member in order to obtain different end positions for the spring, and thus achieve different torque levels. Furthermore, as the spring end is repositioned, the angle at which the spring applies force to the idler pulley changes, thereby further complicating the estimation by the operator of a suitable position for the spring end.
Accordingly, in view of these and other disadvantages, a need exists for an assembly and related technique by which belt tension in a drain cleaning device can be readily adjusted. In addition, it would be particularly desirable if such adjustment could be made concurrently while operating the drain cleaning device.